The conventional single-energy or dual-energy X ray imaging techniques usually use a scintillator-type detector, and signals thus collected reflect a total energy deposition of X rays of multiple colors. An energy deposition is an energy weighted integral of X-ray energy spectrum. Therefore, the imaging result cannot reveal attenuation information of a material under certain energy.
The dual-energy imaging technique comprises CTs of multiple energies, and utilizes different X-ray energy spectrum to perform imaging, and thus may discriminate materials to a certain extent. However, the imaging result has a system error due to the limitation caused by the physical model. Furthermore, there must be an overlapping area between the X-ray energy spectrum, which may affect the capability of discriminating materials.